This PDS-accessible data set contains Cassini magnetic
field data at the highest resolution available as of May, 2012. The MAG
instrument consists of the fluxgate magnetometer (FGM) and helium
magnetometer that is sometimes operated in vector mode (VHM) and sometimes
in scalar mode (SHM). The data for any time may be from any one of these
(a flag indicates which), althought seems to be mostly from FGM. Time
resolution is variable from time to time, ranging at least from 4 vectors/min
to 32 vectors/sec. Nominally, FGM transmits 32 vectors/sec, and VHM and
SHM 2 and 1 vectors/sec, at normal downlink data rate. Magnetic field
Cartesian components are given mostly in RTN coordinates for the Cassini
cruise phase (1999-08-16 to 2004-05-14) and in Kronographic coordinates
at Saturn (>= 2004-05-14). Spacecraft trajectory data are not included
in the data records. These data are expected to be superseded by
Version 3 data to be based on an improved calibration.

The Cassini Radio and Plasma Wave Science (RPWS) calibrated
summary key parameter data set includes reduced temporal and
spectral resolution spectral information calibrated in units of
spectral density for the entire Cassini mission. This data set
includes calibrated values binned and averaged within 1 minute by
0.1 decade spectral channels for all times during the mission
including the two Venus flybys, the Earth flyby, the Jupiter
flyby, interplanetary cruise, and the entire Saturn tour. Data
for this data set are acquired by the RPWS Low Frequency Receiver
(LFR), Medium Frequency Receiver (MFR), and High Frequency
Receiver (HFR). Data are presented in a set of
fixed-record-length tables. This data set is intended to provide
numerical summary data which can be used in conjunction with other
Cassini fields and particles key parameter data sets to establish
trends, select events, or simply as a browse data set for the
Cassini RPWS archive. This data set should be among the first
used by a user of any of the RPWS archive as it will lead one to
information required to search for more detailed or highly
specialized products.

The Cassini Radio and Plasma Wave Science (RPWS) Low Rate Full Resolution Calibrated (RPWS_LOW_RATE_FULL) is a data set including all spectral density measurements acquired by the RPWS in units of electric or magnetic field spectral density. This
data set includes calibrated values for each frequency channel for
each sensor for all times during the mission including the two
Venus flybys, the Earth flyby, the Jupiter flyby, interplanetary
cruise, and the entire Saturn tour. Data for this data set are
acquired from the RPWS Low Frequency Receiver (LFR), Medium
Frequency Receiver (MFR), Medium Frequency Digital Receiver (MFDR)
(which can be used to replace MFR band 2 data) and High Frequency
Receiver (HFR). Data are presented in a set of tables organized
so as to have fixed-length records for ease in data handling.
This data set is intended to be the most comprehensive and
complete data set included in the Cassini RPWS archive. A browse
data set is included with these data which provides for a
graphical search of the data using a series of thumbnail and
full-sized spectrograms which lead the user to the particular data
file(s) of interest. This data set should be among the first used
by a user of any of the RPWS archive as it will lead one to
information required to search for more detailed or highly
specialized products.

Data Set Description
====================
Data Set Description
--------------------
This data set consists of resampled data from the Low Energy
Charged Particle (LECP) experiment on Voyager 1 while the
spacecraft was in the vicinity of Saturn. This instrument
measures the intensities of in-situ charged particles (>26 keV
electrons and >30 keV ions) with various levels of
discrimination based on energy, mass species, and angular
arrival direction. A subset of almost 100 LECP channels are
included with this data set. The LECP data are globally
calibrated to the extent possible (see below) and they are
time averaged to about 15 minute time intervals with the exact
beginning and ending times for those intervals matching the
LECP instrumental cycle periods (the angular scanning periods).
The LECP instrument has a rotating head for obtaining angular
anisotropy measurements of the medium energy charged particles
that it measures. The cycle time for the rotation if variable,
but during encounters it is always faster than 15 minutes.
Thus, the full angular anisotropy information is preserved with
this data. The data is in the form of 'rate' data which has not
been converted to the usual physical units. The reason is that
such a conversion would depend on uncertain determinations such
as the mass species of the particles and the level of
background. Both mass species and background are generally
determined from context during the study of particular regions.
To convert 'rate' to 'intensity' for a particular channel one
performs the following tasks: 1) Decide on the level of
background contamination and subtract that off the given rate
level. Background is to be determined from context and from
making use of sector 8 rates (sector 8 has a 2 mm Al shield
covering it). 2) Divide the background corrected rate by the
channel geometric factor and by the energy bandpass of the
channel. The geometric factor is found in entry
'CHANNEL_GEOMETRIC_FACTOR' as associated with each channel
'CHANNEL_ID'. To determine the energy bandpass, one must
judge the mass species of the of the detected particles (for
ions but not for electrons). The energy band passes are given
in entries 'MINIMUM_INSTRUMENT_PARAMETER' and
'MAXIMUM_INSTRUMENT_PARAMETER' in table 'FPLECPENERGY', and
are given in the form 'energy/nucleon'. For channels that
begin their names with the designations 'CH' these bandpasses
can be used on mass species that are accepted into that
channel (see entries 'MINIMUM_INSTRUMENT_PARAMETER' AND
'MAXIMUM_INSTRUMENT_PARAMETER' in table 'FPLECPCHANZ', which
give the minimum and maximum 'Z' value accepted -- these
entries are blank for electron channels). For other channels
the given bandpass refers only to the lowest 'Z' value
accepted. The and passes for other 'Z' values are not all
known, but some are given in the literature (e.g.
[KRIMIGISETAL1979A]). The final product of these instructions
will be the particle intensity with the units:
counts/(cm^2 str sec keV).
Parameters
==========
Electron Rate
-------------
Sampling Parameter Name : TIME
Data Set Parameter Name : ELECTRON RATE
Sampling Parameter Resolution : 15.000000
Sampling Parameter Interval : 15.000000
Data Set Parameter Unit : COUNTS/SECOND
Noise Level : 0.000000
Sampling Parameter Unit : MINUTE
A measured parameter equaling the number of electrons hitting
a particle detector per specified accumulation interval. The
counted electrons may or may not be discriminated as to their
energies (e.g. greater than E1, or between E1 and E2).
Ion Rate
--------
Sampling Parameter Name : TIME
Data Set Parameter Name : ION RATE
Sampling Parameter Resolution : 15.000000
Sampling Parameter Interval : 15.000000
Data Set Parameter Unit : COUNTS/SECOND
Noise Level : 0.000000
Sampling Parameter Unit : MINUTE
A measured parameter equaling the number of ions striking a
particle detector per specified accumulation interval. The
counted ions may or may not be discriminated as to their
energies (e.g. energy/nucleon or energy/charge between E1 and
E2 or greater than E1) and/or as to their ion composition
(atomic number Z or mass number greater than Z1 or M1, or
between Z1 and z2 or M1 and M2).
Source Instrument Parameters
============================
Instrument Host ID : VG1
Data Set Parameter Name : ION RATE
Instrument Parameter Name : ION RATE
Important Instrument Parameters : 1
Instrument Host ID : VG1
Data Set Parameter Name : ELECTRON RATE

Data Set Overview
=================
Instrument P.I. : John D. Richardson
Data Supplier : John D. Richardson
Data sampling rate : 96 seconds
Data Set Start Time : 1981-08-19T00:00:09.229Z
Data Set Stop Time : 1981-09-04T02:51:21.885Z
This data set contains solar wind plasma browse data near the
Voyager 1 Saturn encounter. Moment parameters are given. Since only
the first 72 or last 72 energy/charge channels are telemetered to
Earth from each M-mode spectra, derived parameters change significantly
only every other set of spectra so the effective time resolution is
96 second.
Parameters
==========
Data Set Parameter 'ION DENSITY'
--------------------------------
Data Set Parameter Name : ION DENSITY
Data Set Parameter Unit : CM**-3
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A derived parameter equaling the number of ions per unit
volume over a specified range of ion energy, energy/charge,
or energy/nucleon. Discrimination with regard to mass and or
charge state is necessary to obtain this quantity, however,
mass and charge state are often assumed due to instrument
limitations.
Many different forms of ion density are derived. Some are
distinguished by their composition (N+, proton, ion, etc.) or
their method of derivation (Maxwellian fit, method of
moments). In some cases, more than one type of density will
be provided in a single data set. In general, if more than
one ion species is analyzed, either by moment or fit, a total
density will be provided which is the sum of the ion
densities. If a plasma component does not have a Maxwellian
distribution the actual distribution can be represented as
the sum of several Maxwellians, in which case the density of
each Maxwellian is given.
Data Set Parameter 'ION TEMPERATURE'
------------------------------------
Data Set Parameter Name : ION TEMPERATURE
Data Set Parameter Unit : EV
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A derived parameter giving an indication of the mean
energy/ion, assuming the shape of the ion energy spectrum to
be Maxwellian. Given that the ion energy spectrum is not
exactly Maxwellian, the ion temperature can be defined
integrally (whereby the mean energy obtained by integrating
under the actual ion energy spectrum is set equal to the
integral under a Maxwellian, where the temperature is a free
parameter for which to solve), or differentially (whereby the
slopes of the actually ion energy spectrum at various energies
are matched to the slopes of a corresponding Maxwellian). The
temperature parameter is often qualified with a range of
applicable energies. Temperatures can be angularly
anisotropic. If the ions do not have a Maxwellian distribution
the actual distribution can be represented as the sum of
several Maxwellians, each with a separate temperature.
Data Set Parameter 'ION THERMAL SPEED'
--------------------------------------
Data Set Parameter Name : ION THERMAL SPEED
Data Set Parameter Unit : KM/S
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A measure of the velocity associated with the temperature of
the ions. It is formally defined as the Ion Thermal Speed
squared equals two times K (Boltzmann's constant) times T
(temperature of ion) divided by M (ion mass). Each component
of a plasma has a thermal speed associated with it.
Data Set Parameter 'ION VELOCITY'
---------------------------------
Data Set Parameter Name : ION VELOCITY
Data Set Parameter Unit : KM/S
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND

Data Set Overview
=================
This data set (VG1-S-PRA-3-RDR-LOWBAND-6SEC-V1.0) contains data
acquired by the Voyager-1 Planetary Radio Astronomy (PRA) instrument
during the Saturn encounter. Since the PRA instrument is able to
observe planetary phenomenon at much larger ranges than other fields
and particles experiments, thus the PRA data cover a variable and
longer encounter period. PRA lowband data provided here cover the
entire Saturn Encounter Phase (1981-06-05 to 1981-09-28).
VG1-S-PRA-3-RDR-LOWBAND-6SEC-V1.0 contains data at the highest
time resolution possible during normal operations. The normal
mode of PRA operations during the planetary encounters was to
sweep through the two radio receiver bands, high band (40.5 to
1.5 MHz in 128 channels spaced 0.3072 MHz apart) and low band
(1326.0 to 1.2 kHz in 70 channels spaced 19.2 kHz apart) in a
period of 6 seconds. The receivers measured, on alternate
samples, the left hand circular and right hand circular (radio
definition) power.
Measured Parameters
===================
The data here are from the low frequency receiver band and are
'packaged' into spacecraft major frame records. Each major
frame is 48 seconds long or eight sweeps through the PRA
receiver. The data are calibrated and are given in units of
'millibels' which is 1000 times the log of the received power.
Zero millbels corresponds to approximately 1.4 x 10^-21 W m^-2
Hz^-1, however, this value is never seen in practice. The
minimum values detected, which includes receiver internal and
spacecraft generated noise, are about 2300 to 2400 millibels,
or about 3.5 x 10^-19 W m^-2 Hz^-1; even higher values are seen
at the very lowest frequencies.
The data format is ASCII and consists of a time indicator
followed by an array containing the eight low band sweeps.
Time is spacecraft event time (SCET) which is basically
universal time at the spacecraft. Specifically, time is in the
form of YYMMDD and seconds into YYMMDD. Both are written as
I6. Example: July 1, 1979 at 12 hours SCET would be 790701,
43200. The seconds corresponds, to the nearest second, to the
start of the sweep (which occurs in PRA high band). The first
value in low band (1326.0 kHz) occurs some 3.9 seconds after
this time and samples at successively lower frequencies are
space 0.03 seconds apart. Only one time is given for the
entire major frame, thus the start of each sweep is the time
given plus 6 times the sweep number minus 1 (i.e., 0 through
7).
The data array is dimensioned as 71 X 8 and written as I4
format (i.e. 568I4). The '8' corresponds to the eight PRA
sweeps. The lowest 68 of the 70 low band channels (1287.6
to 1.2 kHz) are in positions 2-69. Positions 70-71 should be
ignored. Missing or bad data values are set to zero. In
position 1 of each sweep is a status word where the 12 least
significant bits have used, although not all 12 have meaning
for PRA low band. Numbering those bits 0 for least significant
to 11 for most significant, the bits that have meaning are as
follows:
bit
0: 15 dB attenuator in use when equal to 1
1: 30 dB attenuator in use when equal to 1
2: 45 dB attenuator in use when equal to 1
9,10 (together): polarization of first channel sampled
(1326.0 kHz) according to the scheme:
value bit 10 =
0 1
value bit 9 = 0 R L
1 L R
Polarization at successively lower frequencies is opposite to
the frequency above it, i.e. either a LRLR or an RLRL pattern.
Successive 6-second sweeps start on the opposite polarization
as the previous sweep as indicated in the status bits. Note
that this polarization is the received polarization, not
necessarily the emitted polarization. Correct interpretation
of the received polarization depends on the antenna plane
orientation relative to the radio source. A good description
of this concept can be found in [LEBLANCETAL1987].
Missing or bad data values are set to zero. If the status word
is zero, any data in that receiver sweep should be discarded.

Data Set Overview
=================
Data Set Description
--------------------
This data set consists of 4-second edited, wave electric
field intensities from the Voyager 1 Plasma Wave Receiver
spectrum analyzer obtained in the vicinity of the Jovian
magnetosphere. For each 4-second interval, a field strength
is determined for each of the 16 spectrum analyzer channels
whose center frequencies range from 10 Hertz to 56.2
kiloHertz and which are logarithmically spaced in
frequency, four channels per decade. The time associated
with each set of intensities (16 channels) is the time of
the beginning of the scan. During data gaps where complete
4-second spectra are missing, no entries exist in the file,
that is, the gaps are not zero-filled or tagged in any
other way. When one or more channels are missing within a
scan, the missing measurements are zero-filled. Data are
edited but not calibrated. The data numbers in this data
set can be plotted in raw form for event searches and
simple trend analysis since they are roughly proportional
to the log of the electric field strength. Calibration
procedures and tables are provided for use with this data
set; the use of these is described below.
Use of Voyager PWS Calibration Tables
The Voyager PWS calibration table is given in an ASCII text
file named SA_CL.TAB (for Voyager-1). This provides
information to convert the uncalibrated 'data number' output
of the PWS 16-channel spectrum analyzer to calibrated antenna
voltages for each frequency channel. Following is a brief
description of these files and a tutorial in their
application.
Descriptive headers have been removed from the calibration
table file. The columns included are IDN, ICHAN01, ICHAN02,
ICHAN03, ICHAN04, ICHAN05, ICHAN06, ... ICHAN16.
The first column lists an uncalibrated data number followed by
the corresponding value in calibrated volts for each of the 16
frequency channels of the PWS spectrum analyzer. Each line
contains calibrations for successive data number values
ranging from 0 through 255. (Data number 0 actually represents
the lack of data since the baseline noise values for each
channel are all above that.)
A data analysis program may load the appropriate table into a
data structure and thus provide a simple look-up scheme to
obtain the appropriate voltage for a given data number and
frequency channel. For example, the following VAX FORTRAN code
may be used to load a calibration array for Voyager 1 PWS:
real*4 cal (16,0:255)
open ( unit=10, file='SA_CL.TAB', status='old' )
do i=0,255
read (10,*) idn, (cal(ichan,i),ichan=1,16)
end do
close (10)
Then, given an uncalibrated data value idn for the frequency
channel ichan, the corresponding calibrated antenna voltage
would be given by the following array reference:
volts = cal (ichan, idn)
This may be converted to a wave electric field amplitude by
dividing by the effective antenna length in meters, 7.07 m.
That is:
efield = cal(ichan, idn) / 7.07
Spectral density units may be obtained by dividing the square
of the electric field value by the nominal frequency bandwidth
of the corresponding spectrum analyzer channel.
specdens = (cal(ichan,idn)/7.07)**2 / bandwidth(ichan)
Finally, power flux may be obtained by dividing the spectral
density by the impedance of free space in ohms:
pwrflux = ((cal(ichan,idn)/7.07)**2/bandwidth(ichan))/376.73
Of course, for a particular application, it may be more
efficient to apply the above conversions to the calibration
table directly.
The center frequencies and bandwidths of each PWS spectrum
analyzer channel for the Voyager 1 PWS are given below:
VOYAGER 1 PWS SPECTRUM ANALYZER
Voyager-1
Channel Center Frequency Bandwidth
1 10.0 Hz 2.16 Hz
2 17.8 Hz 3.58 Hz
3 31.1 Hz 4.50 Hz
4 56.2 Hz 10.7 Hz

Data Set Overview
=================
Instrument P.I. : Donald A. Gurnett
Data Supplier : William S. Kurth
Data sampling rate : 48 seconds
Data Set Start Time : 1981-08-24T00:00:00.000Z
Data Set Stop Time : 1981-08-31T23:59:12.000Z
Data Set Description
--------------------
This data set consists of 48-second calibrated, averaged wave
electric field intensities from the Voyager 1 Plasma Wave
Receiver spectrum analyzer obtained in the vicinity of the
Jovian magnetosphere. For each 48-second interval, a geometric
average field strength is determined for each of the 16
spectrum analyzer channels whose center frequencies range from
10 Hertz to 56.2 kiloHertz and which are logarithmically
spaced in frequency, four channels per decade. The time
associated with each set of averages is the beginning of the
averaging interval. Averages are stored in units of
volt/meter. During data gaps where complete 48-second
intervals are missing, no entries exist in the file, that is,
the gaps are not zero-filled or tagged in any other way.
Additional information about this data set and the instrument
which produced it can be found elsewhere in this catalog. An
overview of the data in this data set can be found in
[GURNETTETAL1979] and a complete instrument description can be
found in [SCARF&GURNETT1977].
Processing Level Id : 4
Software Flag : Y
Processing Start Time : 1988-02-01
Parameters
==========
Sampling Parameter Name : TIME
Data Set Parameter Name : PLASMA WAVE SPECTRUM
Sampling Parameter Resolution : 48.000000
Minimum Sampling Parameter : 197708201553.000000
Sampling Parameter Interval : 48.000000
Minimum Available Sampling Int : 4.000000
Data Set Parameter Unit : VOLT/METER
Noise Level : 0.000005
Sampling Parameter Unit : SECOND
A set of derived parameters consisting of wave electric field
intensities or electric field spectral densities at various
contiguous frequencies over a range of frequencies. The MKS
units are: Volts/Meter or Volts**2/(Hertz Meter**2),
respectively.
Source Instrument Parameters
============================
Instrument Host ID : VG1
Data Set Parameter Name : PLASMA WAVE SPECTRUM
Instrument Parameter Names : ELECTRIC FIELD WAVEFORM
ELECTRIC FIELD COMPONENT
MAGNETIC FIELD COMPONENT
WAVE ELECTRIC FIELD INTENSITY
WAVE MAGNETIC FIELD INTENSITY
Important Instrument Parameters : 1 (for all parameters)

Data Set Overview
=================
This data set consists of raw data collected during the Titan
radio occultation of Voyager 1 in November 1980 plus ancillary
files that might be useful in analysis of those data. The raw
data are sampled voltage outputs from receivers tuned to the
Voyager carrier frequencies at both S-band and X-band during
the occultations. The data have been reduced to give profiles
of atmospheric temperature and pressure as a function of
height above the surface on both the ingress and egress sides
of Titan [LINDALETAL1983] and to make a marginal detection of
an ionosphere [BIRDETAL1997].
During the Titan occultation, the Voyager 1 spacecraft
provided a coherent, dual-frequency microwave radio signal
source. The signal frequency was derived from a precision,
onboard Ultra-Stable Oscillator (USO). The spacecraft
high-gain antenna (HGA) beamed that signal through the
atmosphere of Titan. As the spacecraft moved on its
trajectory, the radio signal probed different levels in the
atmosphere. An hour later the signals were received by
antennas of the NASA Deep Space Network (DSN) on Earth.
Because the density of Titan's atmosphere was so poorly known
prior to the Voyager encounter, experiment planners did not
know how much refractive bending to expect during the
observations. Models predicted a range of behaviors from very
little bending to so much that the narrow beam from the
spacecraft high-gain antenna (HGA) would be deflected away from
Earth and the surface occultation would not be seen. Timing
uncertainties in the motion of the spacecraft with respect to
Titan only complicated the problem. The experiment was
implemented with a very small (0.11 deg) fixed HGA offset
during the ingress occultation and a large (2.36 deg) offset
during egress. These choices, in retrospect, were very good
given the atmosphere that was found.
Parameters
==========
The output of the S-band receiver was a sinusoidal carrier
signal embedded in noise -- a voltage with bandwidth
approximately 50 kHz and sampled at 300000 samples per second.
The X-band receiver output was similar; but, because of greater
potential for Doppler drift and prediction uncertainty, its
bandwidth was 150 kHz and sampling rate was 300000 samples per
second. Voltages typically were in the range +/- 10 volts;
but the absolute levels were not calibrated. In fact, they
are generally not needed since it is the frequency (or phase)
of the signal (rather than amplitude) that is most useful in
inferring properties of a neutral atmosphere or ionosphere.
The frequency of the USO was known from monitoring during the
Jupiter-Saturn cruise (and from post-Saturn observations).
Doppler contributions from motions of the spacecraft, Earth,
Titan, and other bodies of the solar system were determined
jointly with the Voyager Navigation Team. Relativistic
Doppler contributions could be estimated from proximity to
large masses. Receiver tuning was recorded in POCA
(Programmable Oscillator Control Assembly) files, which are
included with this archive.
Processing
==========
No processing per se has been carried out on these data.
However, because of the high sampling rate, the 8-bit samples
were recorded originally on wide-bandwidth analog video tape.
The analog tapes were then replayed later at slower speeds and
the digital data were extracted and separated onto computer
compatible tapes (CCTs) with S-band and X-band data on
different sets of tapes. Because the S-band data had been
oversampled originally (300 ksps for a 50 kHz bandwidth), only
one of every three samples was saved during the transfer of
S-band data to CCTs. This process, known as 'decimation', meant
that 300 seconds of data could be stored on an S-band CCT
whereas only 100 seconds of X-band data would fit.
Because analog recording technology was required to save the
high data rate digital samples, there are occasional dropouts
in the sample stream. These can be detected by paying special
attention to counter fields in data record headers.
Two analog recorders (A and B) were available at each DSN
complex. Because a single recorder could not capture the
entire set of Titan occultation activities, the two were run
in parallel with staggered start/stop times. Most data were
collected using Recorder A; but Recorder B was used to
capture the samples while Recorder A was being reloaded.
Data
====
Primary data were delivered to Voyager Radio Science Team
members in the form of 30 megabyte (MB) CCTs covering
300 s (S-band) or 100 s (X-band). Each tape had 6000
records of 5056 bytes (56 bytes of header information
and 5000 8-bit samples of receiver output voltage). Tapes
were numbered sequentially as CCTs were generated from the
high density video originals. Tapes with Titan data from
Recorder A were numbered VJ6281 through VJ6360; tapes
from Recorder B were numbered VJ6361 through VJ6380. Test
and calibration data after the Titan encounter were collected
on Recorder A and have numbers VJ6589 through VJ6594.
The original tape numbering has been preserved in the current
file names, which have the form VJnnnnCC.ODR. On tapes where
one or more records could not be read, the original has been
separated into two or more files. The character 'C' indicates
the ordering of these file fragments with 'A' being first (and
the default with no tape reading errors), 'B' next, etc.
Each Original D

Data Set Description
====================
Data Set Description
--------------------
This data set consists of resampled data from the Low Energy
Charged Particle (LECP) experiment on Voyager 2 while the
spacecraft was in the vicinity of Saturn. This instrument
measures the intensities of in-situ charged particles (>26 keV
electrons and >30 keV ions) with various levels of
discrimination based on energy, mass species, and angular
arrival direction. A subset of almost 100 LECP channels are
included with this data set. The LECP data are globally
calibrated to the extent possible (see below) and they are
time averaged to about 15 minute time intervals with the exact
beginning and ending times for those intervals matching the
LECP instrumental cycle periods (the angular scanning periods).
The LECP instrument has a rotating head for obtaining angular
anisotropy measurements of the medium energy charged particles
that it measures. The cycle time for the rotation is variable,
but during encounters it is always faster than 15 minutes.
Thus, the full angular anisotropy information is preserved with
this data. The data is in the form of 'rate' data which has not
been converted to the usual physical units. The reason is that
such a conversion would depend on uncertain determinations such
as the mass species of the particles and the level of
background. Both mass species and background are generally
determined from context during the study of particular regions.
To convert 'rate' to 'intensity' for a particular channel one
performs the following tasks: 1) Decide on the level of
background contamination and subtract that off the given rate
level. Background is to be determined from context and from
making use of sector 8 rates (sector 8 has a 2 mm Al shield
covering it). 2) Divide the background corrected rate by the
channel geometric factor and by the energy bandpass of the
channel. The geometric factor is found in entry
'CHANNEL_GEOMETRIC_FACTOR' as associated with each channel
'CHANNEL_ID'. To determine the energy bandpass, one must
judge the mass species of the of the detected particles (for
ions but not for electrons). The energy band passes are given
in entries 'MINIMUM_INSTRUMENT_PARAMETER' and
'MAXIMUM_INSTRUMENT_PARAMETER' in table 'FPLECPENERGY', and
are given in the form 'energy/nucleon'. For channels that
begin their names with the designations 'CH' these bandpasses
can be used on mass species that are accepted into that
channel (see entries 'MINIMUM_INSTRUMENT_PARAMETER' AND
'MAXIMUM_INSTRUMENT_PARAMETER' in table 'FPLECPCHANZ', which
give the minimum and maximum 'Z' value accepted -- these
entries are blank for electron channels). For other channels
the given bandpass refers only to the lowest 'Z' value
accepted. The and passes for other 'Z' values are not all
known, but some are given in the literature (e.g.
[KRIMIGISETAL1979A]). The final product of these instructions
will be the particle intensity with the units:
counts/(cm^2 str sec keV).
Parameters
==========
Electron Rate
-------------
Sampling Parameter Name : TIME
Data Set Parameter Name : ELECTRON RATE
Sampling Parameter Resolution : 15.000000
Sampling Parameter Interval : 15.000000
Data Set Parameter Unit : COUNTS/SECOND
Noise Level : 0.000000
Sampling Parameter Unit : MINUTE
A measured parameter equaling the number of electrons hitting
a particle detector per specified accumulation interval. The
counted electrons may or may not be discriminated as to their
energies (e.g. greater than E1, or between E1 and E2).
Ion Rate
--------
Sampling Parameter Name : TIME
Data Set Parameter Name : ION RATE
Sampling Parameter Resolution : 15.000000
Sampling Parameter Interval : 15.000000
Data Set Parameter Unit : COUNTS/SECOND
Noise Level : 0.000000
Sampling Parameter Unit : MINUTE
A measured parameter equaling the number of ions striking a
particle detector per specified accumulation interval. The
counted ions may or may not be discriminated as to their
energies (e.g. energy/nucleon or energy/charge between E1 and
E2 or greater than E1) and/or as to their ion composition
(atomic number Z or mass number greater than Z1 or M1, or
between Z1 and z2 or M1 and M2).
Source Instrument Parameters
============================
Instrument Host ID : VG2
Data Set Parameter Name : ION RATE
Instrument Parameter Name : ION RATE
Important Instrument Parameters : 1
Instrument Host ID : VG2
Data Set Parameter Name : ELECTRON RATE

Data Set Overview
=================
Instrument P.I. : John D. Richardson
Data Supplier : John D. Richardson
Data sampling rate : 96 seconds
Data Set Start Time : 1981-08-19T00:00:09.229Z
Data Set Stop Time : 1981-09-04T02:51:21.885Z
This Voyagers 2 data set contains two solar wind plasma data, one
spanning from August 19 to September 4 , 1981, and near encounter
specific data covering August 24-25. Moment parameters are given in
the broader data while the near encounter data is more detailed. The
fit parameters assume a convected isotropic proton Maxwellian
distribution. Use of fit parameters is recommended as these are normally
more accurate. Since only the first 72 or last 72 energy/charge
channels are telemetered to Earth from each M-mode spectra, derived
parameters change significantly only every other set of spectra so
the effective time resolution is 96 second.
Parameters
==========
Data Set Parameter 'ION DENSITY'
--------------------------------
Data Set Parameter Name : ION DENSITY
Data Set Parameter Unit : CM**-3
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A derived parameter equaling the number of ions per unit
volume over a specified range of ion energy, energy/charge,
or energy/nucleon. Discrimination with regard to mass and or
charge state is necessary to obtain this quantity, however,
mass and charge state are often assumed due to instrument
limitations.
Many different forms of ion density are derived. Some are
distinguished by their composition (N+, proton, ion, etc.) or
their method of derivation (Maxwellian fit, method of
moments). In some cases, more than one type of density will
be provided in a single data set. In general, if more than
one ion species is analyzed, either by moment or fit, a total
density will be provided which is the sum of the ion
densities. If a plasma component does not have a Maxwellian
distribution the actual distribution can be represented as
the sum of several Maxwellians, in which case the density of
each Maxwellian is given.
Data Set Parameter 'ION TEMPERATURE'
------------------------------------
Data Set Parameter Name : ION TEMPERATURE
Data Set Parameter Unit : EV
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A derived parameter giving an indication of the mean
energy/ion, assuming the shape of the ion energy spectrum to
be Maxwellian. Given that the ion energy spectrum is not
exactly Maxwellian, the ion temperature can be defined
integrally (whereby the mean energy obtained by integrating
under the actual ion energy spectrum is set equal to the
integral under a Maxwellian, where the temperature is a free
parameter for which to solve), or differentially (whereby the
slopes of the actually ion energy spectrum at various energies
are matched to the slopes of a corresponding Maxwellian). The
temperature parameter is often qualified with a range of
applicable energies. Temperatures can be angularly
anisotropic. If the ions do not have a Maxwellian distribution
the actual distribution can be represented as the sum of
several Maxwellians, each with a separate temperature.
Data Set Parameter 'ION THERMAL SPEED'
--------------------------------------
Data Set Parameter Name : ION THERMAL SPEED
Data Set Parameter Unit : KM/S
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : UNK
Maximum Sampling Parameter : UNK
Sampling Parameter Interval : UNK
Minimum Available Sampling Int : UNK
Noise Level : UNK
A measure of the velocity associated with the temperature of
the ions. It is formally defined as the Ion Thermal Speed
squared equals two times K (Boltzmann's constant) times T
(temperature of ion) divided by M (ion mass). Each component
of a plasma has a thermal speed associated with it.
Data Set Parameter 'ION VELOCITY'
---------------------------------

Data Set Overview
=================
This data set (VG2-S-PRA-3-RDR-LOWBAND-6SEC-V1.0) contains data
acquired by the Voyager-2 Planetary Radio Astronomy (PRA) instrument
during the Saturn encounter. Since the PRA instrument is able to
observe planetary phenomenon at much larger ranges than other fields
and particles experiments, thus the PRA data cover a variable and
longer encounter period. PRA lowband data provided here cover the
entire Saturn Encounter Phase (1981-06-05 to 1981-09-28).
VG2-S-PRA-3-RDR-LOWBAND-6SEC-V1.0 contains data at the highest
time resolution possible during normal operations. The normal
mode of PRA operations during the planetary encounters was to
sweep through the two radio receiver bands, high band (40.5 to
1.5 MHz in 128 channels spaced 0.3072 MHz apart) and low band
(1326.0 to 1.2 kHz in 70 channels spaced 19.2 kHz apart) in a
period of 6 seconds. The receivers measured, on alternate
samples, the left hand circular and right hand circular (radio
definition) power.
Measured Parameters
===================
The data here are from the low frequency receiver band and are
'packaged' into spacecraft major frame records. Each major
frame is 48 seconds long or eight sweeps through the PRA
receiver. The data are calibrated and are given in units of
'millibels' which is 1000 times the log of the received power.
Zero millbels corresponds to approximately 1.4 x 10^-21 W m^-2
Hz^-1, however, this value is never seen in practice. The
minimum values detected, which includes receiver internal and
spacecraft generated noise, are about 2300 to 2400 millibels,
or about 3.5 x 10^-19 W m^-2 Hz^-1; even higher values are seen
at the very lowest frequencies.
The data format is ASCII and consists of a time indicator
followed by an array containing the eight low band sweeps.
Time is spacecraft event time (SCET) which is basically
universal time at the spacecraft. Specifically, time is in the
form of YYMMDD and seconds into YYMMDD. Both are written as
I6. Example: July 1, 1979 at 12 hours SCET would be 790701,
43200. The seconds corresponds, to the nearest second, to the
start of the sweep (which occurs in PRA high band). The first
value in low band (1326.0 kHz) occurs some 3.9 seconds after
this time and samples at successively lower frequencies are
space 0.03 seconds apart. Only one time is given for the
entire major frame, thus the start of each sweep is the time
given plus 6 times the sweep number minus 1 (i.e., 0 through
7).
The data array is dimensioned as 71 X 8 and written as I4
format (i.e. 568I4). The '8' corresponds to the eight PRA
sweeps. The lowest 68 of the 70 low band channels (1287.6
to 1.2 kHz) are in positions 2-69. Positions 70-71 should be
ignored. Missing or bad data values are set to zero. In
position 1 of each sweep is a status word where the 12 least
significant bits have used, although not all 12 have meaning
for PRA low band. Numbering those bits 0 for least significant
to 11 for most significant, the bits that have meaning are as
follows:
bit
0: 15 dB attenuator in use when equal to 1
1: 30 dB attenuator in use when equal to 1
2: 45 dB attenuator in use when equal to 1
9,10 (together): polarization of first channel sampled
(1326.0 kHz) according to the scheme:
value bit 10 =
0 1
value bit 9 = 0 R L
1 L R
Polarization at successively lower frequencies is opposite to
the frequency above it, i.e. either a LRLR or an RLRL pattern.
Successive 6-second sweeps start on the opposite polarization
as the previous sweep as indicated in the status bits. Note
that this polarization is the received polarization, not
necessarily the emitted polarization. Correct interpretation
of the received polarization depends on the antenna plane
orientation relative to the radio source. A good description
of this concept can be found in [LEBLANCETAL1987].
Missing or bad data values are set to zero. If the status word
is zero, any data in that receiver sweep should be discarded.
Data Coverage
=============
Filename Records Start Stop
-----------------------------------------------------------------------
Volume ID: VGPR_1201
PRA_I.TAB 37485 1981-06-05T00:00:07.000Z 1981-06-30T23:59:16.000Z
PRA_II.TAB 31873 1981-07-01T00:00:04.000Z 1981-07-21T23:59:13.000Z
PRA_III.TAB 37592 1981-07-22T00:00:01.000Z 1981-08-13T23:59:12.000Z
PRA_IV.TAB 36831 1981-08-14T00:00:00.000Z 1981-09-07T23:59:58.000Z
PRA_V.TAB 34874 1981-09-08T00:00:46.000Z 1981-09-28T23:59:08.000Z

Data Set Overview
=================
Data Set Description
--------------------
This data set consists of 4-second edited, wave electric
field intensities from the Voyager 2 Plasma Wave Receiver
spectrum analyzer obtained in the vicinity of the Jovian
magnetosphere. For each 4-second interval, a field strength
is determined for each of the 16 spectrum analyzer channels
whose center frequencies range from 10 Hertz to 56.2
kiloHertz and which are logarithmically spaced in
frequency, four channels per decade. The time associated
with each set of intensities (16 channels) is the time of
the beginning of the scan. During data gaps where complete
4-second spectra are missing, no entries exist in the file,
that is, the gaps are not zero-filled or tagged in any
other way. When one or more channels are missing within a
scan, the missing measurements are zero-filled. Data are
edited but not calibrated. The data numbers in this data
set can be plotted in raw form for event searches and
simple trend analysis since they are roughly proportional
to the log of the electric field strength. Calibration
procedures and tables are provided for use with this data
set; the use of these is described below.
Use of Voyager PWS Calibration Tables
The Voyager PWS calibration table is given in an ASCII text
file named SA_CL.TAB (for Voyager-2). This provides
information to convert the uncalibrated 'data number' output
of the PWS 16-channel spectrum analyzer to calibrated antenna
voltages for each frequency channel. Following is a brief
description of these files and a tutorial in their
application.
Descriptive headers have been removed from the calibration
table file. The columns included are IDN, ICHAN01, ICHAN02,
ICHAN03, ICHAN04, ICHAN05, ICHAN06, ... ICHAN16.
The first column lists an uncalibrated data number followed by
the corresponding value in calibrated volts for each of the 16
frequency channels of the PWS spectrum analyzer. Each line
contains calibrations for successive data number values
ranging from 0 through 255. (Data number 0 actually represents
the lack of data since the baseline noise values for each
channel are all above that.)
A data analysis program may load the appropriate table into a
data structure and thus provide a simple look-up scheme to
obtain the appropriate voltage for a given data number and
frequency channel. For example, the following VAX FORTRAN code
may be used to load a calibration array for Voyager 2 PWS:
real*4 cal (16,0:255)
open ( unit=10, file='SA_CL.TAB', status='old' )
do i=0,255
read (10,*) idn, (cal(ichan,i),ichan=1,16)
end do
close (10)
Then, given an uncalibrated data value idn for the frequency
channel ichan, the corresponding calibrated antenna voltage
would be given by the following array reference:
volts = cal (ichan, idn)
This may be converted to a wave electric field amplitude by
dividing by the effective antenna length in meters, 7.07 m.
That is:
efield = cal(ichan, idn) / 7.07
Spectral density units may be obtained by dividing the square
of the electric field value by the nominal frequency bandwidth
of the corresponding spectrum analyzer channel.
specdens = (cal(ichan,idn)/7.07)**2 / bandwidth(ichan)
Finally, power flux may be obtained by dividing the spectral
density by the impedance of free space in ohms:
pwrflux = ((cal(ichan,idn)/7.07)**2/bandwidth(ichan))/376.73
Of course, for a particular application, it may be more
efficient to apply the above conversions to the calibration
table directly.
The center frequencies and bandwidths of each PWS spectrum
analyzer channel for the Voyager 2 PWS are given below:
VOYAGER 2 PWS SPECTRUM ANALYZER
Voyager-2
Channel Center Frequency Bandwidth
1 10.0 Hz 2.16 Hz
2 17.8 Hz 3.58 Hz
3 31.1 Hz 4.50 Hz
4 56.2 Hz 10.7 Hz

Data Set Overview
=================
Instrument P.I. : Donald A. Gurnett
Data Supplier : William S. Kurth
Data sampling rate : 48 seconds
Data Set Start Time : 1981-08-24T00:00:00.000Z
Data Set Stop Time : 1981-08-31T23:59:12.000Z
Data Set Description
--------------------
This data set consists of 48-second calibrated, averaged wave
electric field intensities from the Voyager 2 Plasma Wave
Receiver spectrum analyzer obtained in the vicinity of the
Jovian magnetosphere. For each 48-second interval, a geometric
average field strength is determined for each of the 16
spectrum analyzer channels whose center frequencies range from
10 Hertz to 56.2 kiloHertz and which are logarithmically
spaced in frequency, four channels per decade. The time
associated with each set of averages is the beginning of the
averaging interval. Averages are stored in units of
volt/meter. During data gaps where complete 48-second
intervals are missing, no entries exist in the file, that is,
the gaps are not zero-filled or tagged in any other way.
Additional information about this data set and the instrument
which produced it can be found elsewhere in this catalog. An
overview of the data in this data set can be found in
[GURNETTETAL1979] and a complete instrument description can be
found in [SCARF&GURNETT1977].
Processing Level Id : 4
Software Flag : Y
Processing Start Time : 1988-02-01
Parameters
==========
Sampling Parameter Name : TIME
Data Set Parameter Name : PLASMA WAVE SPECTRUM
Sampling Parameter Resolution : 48.000000
Minimum Sampling Parameter : 197708201553.000000
Sampling Parameter Interval : 48.000000
Minimum Available Sampling Int : 4.000000
Data Set Parameter Unit : VOLT/METER
Noise Level : 0.000005
Sampling Parameter Unit : SECOND
A set of derived parameters consisting of wave electric field
intensities or electric field spectral densities at various
contiguous frequencies over a range of frequencies. The MKS
units are: Volts/Meter or Volts**2/(Hertz Meter**2),
respectively.
Source Instrument Parameters
============================
Instrument Host ID : VG2
Data Set Parameter Name : PLASMA WAVE SPECTRUM
Instrument Parameter Names : ELECTRIC FIELD WAVEFORM
ELECTRIC FIELD COMPONENT
MAGNETIC FIELD COMPONENT
WAVE ELECTRIC FIELD INTENSITY
WAVE MAGNETIC FIELD INTENSITY
Important Instrument Parameters : 1 (for all parameters)

Data Set Overview
================
This data set consists of raw data collected during the Saturn
radio occultation of Voyager 2 on 26 August 1981, ring
scattering data collected during the same time period, test
and calibration data collected about 8 hours earlier, and
ancillary files that might be useful in analysis of those data.
The raw data are sampled voltage outputs from receivers tuned to
the Voyager carrier frequencies at both S-band and X-band during
the occultation. The data have been reduced to give profiles
of temperature and pressure as a function of height in the
atmosphere [LINDALETAL1985] and to infer magnetic field
orientations in the upper ionosphere [HINSON1984].
During the Saturn occultation, the Voyager 2 spacecraft
provided a coherent, dual-frequency microwave radio signal
source. The signal frequency was derived from a precision,
onboard Ultra-Stable Oscillator (USO). The spacecraft
high-gain antenna (HGA) beamed that signal through the
atmosphere and rings of Saturn. As the spacecraft moved on
its trajectory, the radio signal probed the atmosphere and
rings at different radial positions from the center of mass.
An hour later the signals were received using a 64-meter
antenna of the NASA Deep Space Network (DSN) near Canberra
(Australia).
To keep the refracted radio beam aimed toward the DSN antenna
during the atmospheric occultation, the spacecraft attitude
was adjusted so that the high-gain antenna (HGA) was pointed
at the virtual image of Earth on Saturn's limb. This ensured
that maximum signal strength would be available from the
deepest probing. During the deepest part of the atmospheric
occultation, the HGA was pointed toward the rings to determine
whether signals forward scattered by the ring particles could
be detected on Earth.
Related data sets of possible interest include:
DATA_SET_ID Description
----------------------- --------------------------------
VG1-SSA-RSS-1-ROCC-V1.0 Titan radio occultation raw data
VG1-S-RSS-1-REDR-V1.0* Saturn Voyager 1 ingress radio
occultation raw data
VG1-S-RSS-1-ROCC-V1.0 Saturn Voyager 1 egress radio
occultation and ring
scattering raw data
*tentative DATA_SET_ID assignment
Parameters
==========
The output of each S-band receiver was a sinusoidal carrier
signal embedded in noise -- a voltage with bandwidth
approximately 50 kHz and sampled at 300000 samples per second.
The X-band receiver output was similar; but, because of greater
potential for Doppler drift and prediction uncertainty, its
bandwidth was 150 kHz and sampling rate was 300000 samples per
second. Voltages typically were in the range +/- 10 volts;
but the absolute levels were not calibrated. In fact, they
are generally not needed since it is the frequency (or phase)
of the signal (rather than amplitude) that is most useful in
inferring properties of a neutral atmosphere or ionosphere,
and amplitude calibration for ring observations can be
obtained by referencing signals to the background radiothermal
noise in the data stream.
The frequency of the USO was known from monitoring during the
Jupiter-Saturn cruise (and from post-Saturn observations).
Doppler contributions from motions of the spacecraft, Earth,
Saturn, and other bodies of the solar system were determined
jointly with the Voyager Navigation Team. Relativistic
Doppler contributions could be estimated from proximity to
large masses. Receiver tuning was recorded in POCA
(Programmable Oscillator Control Assembly) files, which are
included with this archive.
Processing
==========
No processing per se has been carried out on these data.
However, because of the high sampling rate, the 8-bit samples
were recorded originally on wide-bandwidth analog video tape.
The analog tapes were then replayed later at slower speeds and
the digital data were extracted onto computer compatible tapes
(CCTs) with each receiver channel on a separate set of tapes.
Because the S-band data had been oversampled originally
(300 ksps for a 50 kHz bandwidth), only one of every three
samples was saved during the transfer of S-band data to CCTs.
This process, known as 'decimation', meant that 300 seconds
of data could be stored on an S-band CCT whereas only
100 seconds of X-band data would fit.
Because analog recording technology was required to save the
high data rate digital samples, there are occasional dropouts
in the sample stream. These can be detected by paying special
attention to counter fields in data record headers.
Two analog recorders (A and B) were available at each DSN
complex. Because a single recorder could not capture the
entire set of Saturn occultation activities, the two were run
in parallel with staggered start/stop times. Most data were
collected using Recorder A; but Recorder B was used to
capture the samples while Recorder A was being reloaded.
Data
====
Primary data were delivered to Voyager Radio Science Team
members in the form of 30 megabyte (MB) CCTs covering
300 s (S-band) or 100 s (X-band). Each tape had 6000
records of 5056 bytes (56 bytes of header information
and 5000 8-bit samples of receiver output voltage). Tapes
were numbered s